Glossary

accelerated perspective - the use of exaggerated perspective effects in architecture to give an enhanced sense of spatial depth.

aerial perspective - the impression of depth created by the reduction in contrast of objects in the distance, which is caused by atmospheric haze.

anamorphosis - an image that has been distorted, so that it can only be seen correctly when viewed from a specific point.

artificial perspective - a term for perspective drawings that are based on Albertian principles (in contrast to 'synthetic perspective').

centre line - the line leading from the viewpoint to the point on the picture plane that is directly in front of the viewer's eye.

cone of vision - the cone of visual rays that converge at the eye or 'viewing position'.

Construzione Legittima - the term used by Alberti to describe his method of perspective construction.

crate - a notional orthogonal box placed around a complex object to make it easier to draw.

curved picture plane - a cylindrical or spherical picture plane, used in an attempt to more accurately depict an image as it would appear to the eye, or to emulate a fish-eye camera lens.

cylinder anamorphosis - an image that has been distorted, so that it can only be seen correctly when viewed reflected in a cylindrical mirror.

diagonal perspective - a perspective view that looks diagonally towards the principal surfaces of an object.

diagonal vanishing point (DVP) - the point on the horizon towards which any diagonal lines in the object will converge.

distance point - another term for a diagonal vanishing point.

distortion - a term used to describe the 'unnatural' appearance of objects when drawn in perspective, particularly when wide angles of view are used.

eye point - the point on the picture plane that is directly in front of the viewer's eye. The eye point is always on the horizon.

horizon - the notional horizontal line in the far distance, dividing the earth from the sky.

horizon line - in a perspective drawing, this is a horizontal line at eye level. Vanishing points for all horizontal edges will be on the horizon line.

linear perspective - an alternative term for 'artificial perspective'.

natural perspective - an alternative term for 'synthetic perspective'.

non-parallel perspective - an alternative term for 'diagonal perspective'.

object centred - a drawing system based on representing an object without reference to a specific experiential viewpoint. Plans, sections, elevations and axonometrics are all form of object centred drawings.

one-point perspective - a common term for 'parallel perspective', (although the drawing may in fact include more than one vanishing points).

parallel perspective - a perspective view that is aligned in parallel with the principal surfaces of an object.

perspective 'window' - an alternative term for the 'picture plane'.

picture plane - the notional intersection of the visual cone on which the position of the visual rays are plotted.

retinal image - a notional description of how a view may appear on the retina of the eye.

sciagraphical perspective - the projection of shadows in perspective.

spectator point - see 'viewing position'.

synthetic perspective - drawings based on a curved picture plane.

two-point perspective - a common term for diagonal perspective (although the drawing may in fact include more than two vanishing points).

vanishing point (VP) - a point on the horizon towards which a set of parallel lines will converge.

vertical datum - an intersection of the object with the picture plane at which a vertical scale can easily be determined.

viewer centred - a drawing system, based on a spectator's viewpoint. A perspective drawing is one type of viewer centred system.

viewing distance - the distance between the spectator and the object depicted or picture plane.

viewing position - the fixed view point from which a perspective view is constructed.

viewpoint - see 'viewing position'.

visual pyramid - the cone of visual rays that converge at the eye or 'viewing position'.

visual rays - a straight line, running from a point on an object to the eye.